The present embodiments relate to securely providing a receiver unit with a replica pseudo-random noise code.
Pseudo-random code sequences (e.g., pseudo-random noise codes or pseudo-random number codes (PRNC or PRN codes for short)) are used during radio transmission, for example. These are spreading codes that spread the frequency of a message signal. As a result of the broadband transmission, such a signal has a high degree of robustness to interference. Spreading sequences are used, for example, in satellite navigation systems such as GPS, Glonass, Beidou or Galileo. In this case, the emitted satellite signal is below a noise level. A receiver may decode the emitted signal only by correlation with an appropriate PRN code that is available to the receiver. This may be the identical PRN code that may already be present in the receiver, for example. It is also possible to refer to a replica PRN code that is a reconstructed or simulated PRN code or a PRN code in the form of a second embodiment.
It is known practice to use cryptographic PRN codes. In this case, the code sequence is dependent on a cryptographic key. A receiver may generate the appropriate PRN code for decoding the reception signal only if the receiver knows the PRN code used by the transmitter to emit the signal. The receiver requires the cryptographic key for this purpose.
In this case, the receiver (e.g., the signal processing in the receiver) may be protected from attackers in a complicated manner using security mechanisms. For example, an FPGA in which the cryptographic signals are processed are to be expensively protected using emission protection or tamper protection.
It is generally known practice to digitize and record raw data of a received GPS signal. The raw data is transmitted to a cloud service, with the result that the signal processing is implemented on a server. In this case, the server may be specially protected, with the result that the cryptographic signal processing that is critical to security is carried out in a secure computing center. However, a large proportion of the server environment, including data transmission paths used, is again to be protected in a complicated manner.
The intention is for it to be as difficult as possible for an attacker to gain possession of a PRN code that is generated and provided at the receiver end. This is also intended to be provided for the situation in which the attacker may access a receiver and attempts to manipulate the receiver.